How to conduct the Threshold Test of Mobile Equipment specified in 3rd edition?

Roland chung

Trusted Information Resource
As we know, 3rd edition has added a new test for mobile equipment more than 45 kg. That is threshold test.

I believe that such new requirement is reasonable and foreseeable. However, the test method requires all wheels and castors are to impact a obstruction (20 mm high and 80 mm wide) at a speed of 0,4 m/s ± 0,1 m/s for manual mobile equipment. It seems hard to conduct this test in reality. How to maintain the speed of 0,4 m/s during the whole test is critical.

I've heard some people including test houses said that the method for threshold test is not realistic and deviates from the theory of mechanics. I think if this really is a mistake in standard, IEC committee shall modify it in the A1. But there is no technical change for the threshold test in A1(draft).

Who have experience with the threshold test, please kindly share your knowledge.
 

Stijloor

Leader
Super Moderator
As we know, 3rd edition has added a new test for mobile equipment more than 45 kg. That is threshold test.

I believe that such new requirement is reasonable and foreseeable. However, the test method requires all wheels and castors are to impact a obstruction (20 mm high and 80 mm wide) at a speed of 0,4 m/s ± 0,1 m/s for manual mobile equipment. It seems hard to conduct this test in reality. How to maintain the speed of 0,4 m/s during the whole test is critical.

I've heard some people including test houses said that the method for threshold test is not realistic and deviates from the theory of mechanics. I think if this really is a mistake in standard, IEC committee shall modify it in the A1. But there is no technical change for the threshold test in A1(draft).

Who have experience with the threshold test, please kindly share your knowledge.

Can someone help with this?

Thank you very much!

Stijloor.
 

Pads38

Moderator
Hi Roland

I have been thinking over this one. We haven't (yet) had to do this test but I have a couple of ideas. They are not what you could call 'calibrated' but they might allow you to show your auditor that the risk involved is very low, which might be satisfactory.

1. Mark out a test strip (say 5 metres) with an 'acceleration' zone before it. Practice pushing the device through the zone at 0.4m/s using a metronome to time your steps. If you can pass through the marked zone in the right time, say 10 times in a row (plus or minus a few percent) you could be reasonably confident that you can repeat it again. Now introduce your step and see what happens.

Now if you could show that the device has not fallen over or suffered damage when the test has been repeated several times (perhaps bracketing the speed, say 0.2 - 0.6 m/s) then you could be confident that the test would not be a problem. Similarly, if it fell over every time you probably have a problem.

2. Second idea was to tie a rope to the device and tow it through the measured zone by wrapping the tow rope around a drum of known circumference. Now your speed will be set by the revolution speed of the drum which could be measured by a simple optical sensor.

With these simple tests you could show either a clear pass or a clear fail. If you found the results marginal you would then have to explore more controlled (and expensive) testing.

Hope these ideas help.

Pads
 

Pads38

Moderator
Another idea;

Mark out a scale on the floor then use a video camera from above to capture the passage of the device past the marks. Use video editing software to find out the time taken to pass the marks. This allows you to have a record of the actual speed achieved.
 
N

nikolaos

Hi Roland,

I know nothing about the dimensions, shape and weight of the equipment you are asking ideas of how to perform the treahold test.
This is our experiance with our device. Our problem was not how to perform but how pass the test. H=1000mm, W=500mm, D=600mm, 60Kg of weight and with 4 wheels. Theoretical mechanical calculations using the virtual work principle, demostrated that the wheels must have 920mm of diameter to pass the test and this is totally absurd. I realy doubt the competence of the guys that introduced this test to the standard.
 

Roland chung

Trusted Information Resource
Hello nikolaos,

Could you show me the testing method you employed and the theoretical mechanical calculation?
 
N

nikolaos

Hello nikolaos,

Could you show me the testing method you employed and the theoretical mechanical calculation?

We conducted the test according the IEC/TR 62354 Ed. 2.0 Draft. Here is how you can do it:
Affix on a hard flat horizontal floor a 20mm high by 80mm wide threshold
Use a ruler to measure a distance of 4mm (or any distance you prefer)
Calculate the time needed to cover the distance at 0,4m/s
Pushing the equipment at a height of 1m (or at the highest point if it is less than 1m) to reach the threshold at the calculated time (10s for 4m disrance). If it passes over the threshold or does not overbalance the test is pass, otherwise is fail. If it fails consider to modify the mechanical design, if this is not possible there is one more think you can do: classify your equipment as transportable/portable. There are some other test to do but are easier to pass. In the user manual you can write use the handles (if any) to pass over a threshold and/or the equipment is to be moved by two or more persons. I am confident that any NB will accept it.
Of course are these are general indications as I have no idea how is you equipment.
The Test report calculation is only for internal use because there is a detailed description of the mechanics and I can not post it here.
Hope this helps you
 

Roland chung

Trusted Information Resource
Hello nikolaos,

Thanks for your input. Actually, the testing procedure in IEC/TR 62354: 2009 does not help, since IEC/TR 62354 just copied the text of IEC 60601.

I do not think our equipment can be classified as portable. It is a mobile ultrasonic diagnostic scanner with 4 wheels and a handle bar. The manual actually has stated that more than 2 persons are needed when transported the scanner.

The body dimension of scanner: H=1500mm, W=450mm, D=900mm. What diameter of wheels is suitable for threshold test?

Thanks.
 
N

nikolaos

Hello Roland,

Have you tried to do the test? what was the result?
Your equipment is a little bigger than ours but are similar. In our case we need about 1000mm!!! wheels, actualy they are 100mm of diameter. Probably you need bigger wheels, but I suppose that this is impossible. There are many quantities to consider to calculate the exact diameter of the wheels.
Our device is a blood cell separator and we can classify it as transportable/portable, why you can not? Have you discussed this with your NB?
 
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